Origin of the large low shear velocity provinces (LLSVP) in the bottom of the lower mantle has been a mystery in Earth science for a long time. In this collaborative work, our CIDER team (leader Johnny Zhang) proposes that small quantities of Fe-Ni-S metallic liquid that were trapped during the crystalization of early magma ocean could explain the observed properties of the LLSVP. This provides a new mechanism for generating large-scale chemical heterogeneities in Earth's early history.